Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$241.93	13.733%	$275.1542	$275.15	$275.15	$275.20
Purchase #2	$209.47	9.720%	$229.8305	$229.83	$229.85	$229.80
Purchase #3	$30.89	12.733%	$34.8232	$34.82	$34.80	$34.80
Purchase #4	$225.89	13.557%	$256.5139	$256.51	$256.50	$256.50
Purchase #5	$215.31	7.537%	$231.5379	$231.54	$231.55	$231.50
Purchase #6	$142.88	13.503%	$162.1731	$162.17	$162.15	$162.20
Purchase #7	$12.94	10.819%	$14.34	$14.34	$14.35	$14.30
7 purchase totals =	$1,079.31		$1,204.3728	$1,204.36	$1,204.35	$1,204.30